pressure switch

[groupagt4]

i need a pressure switch that will give power to a soleniod that opens a extra fuel feed to my carb when boost reaches about 5 psi. anyone have a idea where i can get one, adjustable would be best

[Akane]

What you need is a Hobbs switch, google for it for more info.

[Crampy]

You could use a MAP sensor from a Turbo car and make up a circuit to suit. Put the output of the MAP sensor into the "+" input of a comparator circuit. Easily adjusted with a variable resister to change the reference voltage to the "-" input to the comparator.

Eg, when the MAP voltage (eg boost level) gets above the preset amount (eg 5 psi set with the reference voltage), the output of the comparator swithes on.

Then use the output of the comparator to drive a transistor (or relay) to engage the solenoid.

Easy.

[strx7]

pretty sure your nearest electrical components supplier ie: J A RUSSELL sell pressure switches which do the job

[matt dunn]

I can supply a hobbs pressure sw,

but they are close to $100 from memory,

OR,

Use an oil pressure switch ($19) and a change over relay. ($10)